Pressure reducing device for refrigerating apparatus



P 1951 H. M. GOLDBERG 2,568,123

PRESSURE REDUCING DEVICE FOR REFRIGERATING APPARATUS Filed July 25, 19502 Sheets-Sheet 1 48 FIG.2

as 54 2 58 INVENTOR:

+ l-JERMAN M.GOLDBERG MW awxywwz ATT'YS Sgpt. 18, 1951 PRESSURE REDUCINGDEVICE FOR REFRIGERATING APPARATUS Filed July 25, 1950 2 Sheets-Sheet 2m 5 i 4 '0 so I47 I L I no I:

no me 21' s| lna FIG. 3 I50 s A A "a m INVENTOR. I: ERMAN M .GOLDBERG H.M. GOLDBERG 2,568,123

Patented Sept. 18, i951 PRESSURE REDUCING DEVICE Fort REFRIGERATINGAPPARATUS Herman M. Goldberg, Chicago, Ill-., assignor to StandardRefrigeration Company, Inc., Chicago, Illa, a corporation of IllinoisApplication July 25,1950, Serial No. 175,813

1 claim. 1

The present invention relates to refrigeration systems and moreparticularly to improved means for controlling the flow of refrigerantfrom the high to the low pressure sides of the system;

This application is a continuation in-partof my copending application,Serial No. 87,815,1iled April 15, 1949, now Patent Number 2,532,019,issued November 28, 1950, for Pressure Reducing Device for RefrigeratingApparatus.

Present day refrigerating systems invariably employ some type ofrestricting or regulating device for the purpose of controlling the flowof refrigerant through the system from the high pressure condenser orcompressor phase thereof to the low pressure expansion phase thereof.Various types of regulating devices in the form of expansion valves havebeen employed for this purpose as well as the use of so-called capillarytubing. The many valve structures employed are found to be expensive tomanufacture and delicate in operation and therefore unreliable, whilethe capillary tubing frequently becomes clogged due to the accumulationof foreign matter in the refrigerant or due to Settling out of anyexisting solid particles in the refrigerant "after a prolonged period ofdisuse of the system. Moreover, conventional, so-called, capillarytubing has an inside diameter that is exceedingly small so that it isdifficult, and sometimes impossible, to clean so that replacementthereof is usually the only solution when clogging occurs. Still fur=ther, because of the small internal dimension of such capillary tubing,uniformity of dimension within any given length of tubing is diflicultto attain and precise regulation of the flow of fluid therethrough is acut-and-try matter. Thus, in the manufacture of refrigerating units, asfor example, household refrigerators or the like, on a large scale, apredetermined length of capillary tubing is determined upon by aout-and-try method to best accommodate a particular test unit of givenspecifications, and thereafter a large number of the capillary tubes orcoils are cut from tube stock for installation in an equal number ofassembly line units. Because of the nonuniformity in the internaldimensions of the stock tubing, and because of non-uniformity in thebending or coiling operation when the tubing is actually applied to andinstalled in the various units, varying flow characteristics areattained in the assembled units and unsatisfactory performance in alarge percentage of the units may be expected.

The present invention is designed to over- 2 are attendant upon the useof present day restricting devices, particularly upon the use of theso-called capillary tubing, and toward this end it contemplates theprovision of a restricting device which embodies the same principle ofoperation as does ordinary capillary tubing. in

that it affords a relatively long, restricted path of flow for therefrigerant, but which at the same time is capable of disassembly forthe purpose or cleaning the various parts thereof to remove any foreignmaterial so that upon reassembly of the parts the original restrictedpath of flow for the refrigerant may be reestablished.

The provision of a restricting device of the character briefly outlinedabove being one of the principal objects of the invention, another andequally important object thereof is to provide such a device in whichthe length of the capillary path for the fluid, and consequently theamount of refrigerant flowing through the device may be adjustablycontrolled to any desired degree to attain the desired pressure. dropbetween the high and the low pressure sides of the system, or, in otherwords, at the cooling coils thereof.

A further disadvantage attendant upon the use of conventional so-calledcapillary tubing in pressure regulating systems arises where shippingproblems are involved. Where new installations in the form of completeassembled refrigerators, as for example, household refrigerators,

deep freeze units and the like, are shipped from the factory to theirvarious destinations, loss of refrigerant frequency occurs at the pointsof connection or joints at which the capillary tubing is connected toother parts of the closed fluid system. Such loss of fluid due toleakage frequently is a result of vibration or shock arising either intransit or during the process of unpacking of the unit at itsdestination. Because of such difiiculties, many manufacturers have foundit expedient to ship the units to the dis tributors in dry conditionwhile the distributors, in turn, deliver them to the customer in thesame condition, relying upon the service or 7 installation worker tosupply the necessary refrigerant at the scene of ultimate installation.

Alternatively, in an effort to overcome the above-noted limitation thatis attendant upon the manufacture and installation of refrigeratingunits, some manufacturers have developed a system. Such a procedure hasnot been entirely satisfactory in actual practice inasmuch as partialdisassembly of the system, or at least uncoupling of certain partsthereof is necessary to render the puncturable seal accessible and,before reassembly of the parts can be made, considerable loss ofrefrigerant may result. Furthermore, manual puncturing of the seal mayleave an opening of undetermined size which acts as a restriction to theflow of refrigerant and, ad-- ditionally, such puncturing may lead tothe presence of particles of the sealing material or compound within theclosed system.

It is therefore another important object of the present invention toprovide an improved regulating device of the character briefly outlinedabove in which the same adjusting means which is employed for varyingthe length of the fluid path through the device may also be employed toeffect complete blocking off of the fluid path at one end thereof sothat leakage of the refrigerant from the device is effectivelyprevented, thus enabling the manufacturer to supply the refrigerationunits in filled condition preparatory to instant use thereof at thescene of installation 4 upon completion of a minor adjustment operationon the part of the installation worker or of the purchaser.

Another and related object of the invention is to provide a restrictingunit of this character in which the necessary adjustment for placing theinstallation in immediate service may be made from a convenient pointadjacent and. outside of the restricting unit without requiring partialor complete disassembly thereof and by the use of ordinary tools.

A still further object of the present invention is to provide arestricting device having the engineering and physical characteristicsof both a restrictor valve as well as of capillary tubing and which mayreadily constitute a built-in part of an evaporator unit associated witha refrigerating system.

Additional objects of the invention are, in general, the same as thoseset forth in my above mentioned copending application of which this is acontinuation, while still other objects and advantages of the invention,not at this time enumerated will become more readily apparent as thenature of the invention is better understood.

The accompanying two sheets of drawings illustrate two selectedembodiments of the invention, and the views thereof are as follows:

Fig. 1 is an elevational view of an evaporator unit embodying one formof the improved refrigerant restrictor device forming a part of thepresent invention;

Fig. 2 is an enlarged detail longitudinal sectional view takensubstantially through the restrictor valve of Fig. 1;

Fig. 3 is a further enlarged detail fragmentary sectional view takensubstantially through the inlet end of the restrictor device;

Fig. 4 is a transverse sectional view taken substantially along the line44 of Fig. 3;

Fig. 5 is an elevational view similar to Fig. 1 of an evaporator unitembodying a modified form of the improved restrictor device comprisingthe present invention;

Fig. 6 is an enlarged sectional view taken substantially centrallythrough the restrictor device of Fig. 5;

Fig. 7 is a further enlarged fragmentary sectional view takensubstantially centrally through the outlet end of the restrictor device;and

Fig. 8 is a sectional view taken substantially along the line 88 of Fig.'7. I

For the purpose of illustration, the improved restricting device of thepresent invention, and of which two forms have been illustrated herein,is shown as employed in connection with an evaporator unit, of which itmay constitute a built-in part, for regulating the flow of refrigerantfrom the high side of the system to the low side thereof. In otherwords, the restricting device, forming the subject matter of thisinvention, may be used to advantage for controlling the flow ofrefrigerant from the compressor or condenser phase of the system to theexpansion phase thereof.

Referring now to Figs. 1 to 4 inclusive, wherein one form of theinvention has been illustrated,

the restricting device is designated in its entirety at If] and mayconstitute a built-in part of an evaporator unit i2 of more or lessconventional design and having associated therewith the usual expansionor refrigeration coil l4 constituting, in part, the low pressure phaseof the system. The restricting device I9 is generally of tubular designand has its outlet end connected as indicated at l6 with therefrigeration coil I4, while its inlet end may be connected as indicatedat l8 with a tube 29 leading from a compressor or condenser unit (notshown) constituting, in part,

the high pressure phase of the system.

The restrictor device l0 involves in its general organization anelongated tubular body or cylinder 22 having an axially extending mainbore 24 which is provided with internal screw threads 28 throughout itsentire length. The threads 26 are of V-shape in cross section andprovide relatively sharp, deep troughs 28 therebetween and haverelatively sharp V-shaped crests 30 (see particularly Fig. 3). Thecylinder 22 may have external screw threads 32 at its inlet end toreceive thereover the internal threads 34 formed within a cap member 36.The cylinder 22 is formed with a closure wall 38 at its outlet end whichhas formed integrally therewith an outwardly projecting nipple 40 havingan axial bore 42 communicating with the main bore 24 of the cylinder 22.The nipple 40 may be formed with an external friction surface 44 whichis adapted to receive thereover the expanded end of the refrigerationcoil l4 to provide the fluid tight connection [6.

The V-shaped threads 26 in the valve cylinder 22 are adapted to engagescrew threads 46 formed externally on an elongated internal rod 48,which may be positioned within the main bore 24. The threads 46 on therod 48 are provided with V- shaped troughs 50 therebetween and flatcrests 52. The threads 46 may be formed in any suitable manner, as forexample by cutting V-shaped threads on the plug and then grinding downthe sharp crests thereof to produce the flat crests 52. The interfittingof the flat crests 52 of the threads 46, with the sharp V threads 26forms a slender spiral capillary passage 54 which is generallytriangular in cross section. This passage 54 affords a uniformlyrestricted passage for the flow of refrigerant as the same progressivelyflows from the inlet end of the device to the outlet end thereof.

Means are provided for permitting or effecting adjustment of the lengthof the passage 54 and this means includes a counter-bore 56 which isformed in the inlet end of the cylinder 22, the counter-bore 56 beingcoaxial with the main bore inder 22 at the inner end of the counter-bore56 and provides the means for adjusting the length of the spiral passage54, in that the degree of penetration of the rod #8 within the main bore2% and beyond the shoulder or step 53 directly determines the amount ofrestriction oifered to the flow of the refrigerant. The length of thespiral restricting passage 54 increases, therefore, when the rod E3 isthreaded into the main bore 24, and decreases when the rod is threadedoutwardly from the main bore.

A seal or washer 60 may be positioned between the cap member 36 and theinlet end of the cylinder 22 to provide a fluid tight seal between thecylinder and the cap member.

' The cap member 36 is provided with an axially aligned threaded nipple62 which projects outwardly therefrom and is adapted to threadedlyreceive thereover an internally threaded closure cap 64. A passage'filiextending axially through the cap 36 and through the nipple s2 permitsinsertion of a screw driver or other tool therethrough upon removal ofthe cap for engagement with a slot El formed in the proximate end of therod 48. Thus by rotating the threaded rod d8 Within the cylinder 22 inone direction or the other, the length of the spiral restricted passage54 and, consequently, the flow and pressure drop of the refrigerantfluid passing through the restricting device may be regulated after thesystem has been placed in operation.

A seal washer "It may surround the nipple 62 'to form a fiuid tight sealbetween the closure cap 64 and the cap 36 when the former is threaded onthe nipple 62.

An inclined passage 12 through which refrigerant may enter the device isformed in the cap member 36. This passage 12 communicates with andextends laterally from the passage 66. The passage 72 may have asuitable screening material M, such as wire gauze, inserted therein forthe.

purpose of separating foreign or extraneous matter from the refrigerantbefore it passes through the restricting device so that the device willnot become clogged. The screening material 14 may be removed from thepassage 34 from time to time so that it may be cleaned or replaced withnew, screening material.

The end of the tube 20 leading from the high pressure stage hascommunication with the passage !2 and may be joined to the cap member 36by any suitable means as, for example, by soldering or the like.

The rod 88 may be solid, but it is sometimes desirable that it be ofhollow construction and provided with a longitudinally extending bore'16 which is closed at one end and which communicates with the spaceexisting within the cylinder 22 at the outlet end thereof. Thus, thebore 16 and space just referred to constitute, in effect,

-an expansion chamber 78 at the outlet end of the spiral passage 54which permits the refrigerant fluid to expand to a greater extent thanif the .rod as were solid so that the temperature drop of the expandingrefrigerant will be appreciably greater. It is not altogether necessary,however, that the rod 48 be provided with the bore 16 as it may besolid, whereby the space or chamber 78 alone may be used for expansionof the refrigerant.

The pressure reducing or restricting device I0 serves as an extremelyeffective means for controlling the flow of refrigerant entering theexpansion coil i l of the evaporator unit l2. Liquid refrigerant underpressure from the usual compressor or condenser of the refrigerantsystem,

enters the passage 12from the tube 20 and-passes through the screeningmaterial 14 where any foreign matter which might be intermixed with therefrigerant is screened or separated therefrom. The liquid refrigerantthen flows through the passage 66 and thence into the counter-bore 56 inthe cylinder 22. Upon arriving at the shoulder 58 at the inlet end ofthe counter-bore the refrigerant enters and progresses through thespiral passage 54 formed between the screw threads 26 and 46 in thecylinder 22 and on the rod, respectively. The pressure of therefrigerant is reduced progressively as the refrigerantfiows through thepassage 54, the amount of pressure drop being determined by the depth ofpenetration of the plug or rod 48 in the threaded bore of the cylinder22.

As the liquid refrigerant reaches the end of the spiral passage 54 itexpands immediately into the space or chamber 18- and into the bore 16formed in the rod 48. The expanded refrigerant thus changes into itsgaseous state and then flows through the bore 42 and into the expansionor refrigeration coil [4 where it further expands and absorbs heat fromthe surrounding atmosphere. By the time the: gaseous refrigerant reachesthe end of its passage through the coil l4 it has absorbed considerableheat from the surrounding atmosphere and it is then drawn into thecompressor where it is condensed back into its liquid state.

From the above description it will be seen that, the invention comprisesa restricting device which. can be used with any type of refrigerant,since. any desired pressure drop may be made by proper adjustment of theposition of the rod 48 in the main bore 24 of the cylinder 22. Thedevice may be easily disassembled for cleaning by first removing the capmember 36 from the cylinder 22 and then removing the threaded rod 48from thebore 24 of the cylinder 22.

Many additional advantages arise by utilizing; a device of the typeembodied in the invention. Vibration noises which are familiar tocapillary tube installations are eliminated, whether the: device is usedwith a household standard temperature unit or with a plate type lowtemperature refrigeration unit. This novel type of evaporator unithaving a built-in pressure reducing valve: balances the load on thecompressormotor on. the off-cycle. Motors having low starting. torquesmay be used because of this balancing. feature, therefore, and the costof manufacturing; the refrigeration system is correspondingly lowered.Also, the use of the present unit eliminatesthe use of a liquidreceiver, and thereby less refrigerant is used or required forsuccessful operation.

Referring now to Figs. 5 to 8 inclusive, wherein a modified form of theinvention is illustrated, the restricting device 1 it is shown asconstituting a built-in unit of an evaporator H2, similar to the unit l2of Fig. l, and having a refrigerating or expansion coil I Hi associatedtherewith.

The restricting device iii! involves in its general organization anelongated tubular body, casing or cylinder i it having a threaded boreH8 formed therein adjacent its outlet end and an axially communicatingcounter-bore are adjacent its inlet end. The threaded bore Eli!communicates at the extreme outlet end of the cylinder with anoutletport I22 which, in turn, communicates with one end of the coolingor refrigerating coil H4 which is preferably received Within a socketI24 provided in the end of the cylinder and which may be suitablysecured therein by a welding or other operation. The cylinder H6 isformed with a substantially conical seating surface I26 in the vicinityof the outlet port I22 and which surrounds the latter for a purpose thatwill be set forth presently.

The counter-bore I at the inlet end of the cylinder H6 is provided witha laterally or radially extending inlet port I28 which is maintained insealing relationship with one end of a tube or conduit I30 leading fromthe compressor or condenser stage of the refrigerating system. Thethreads which are formed in the bore H8 of the cylinder II6 aredesignated at I32 and are V-shaped in cross section and providerelatively deep trough portions I34 therebetween and relatively sharpcrest portions I35. The threads I32 are adapted to engage mating screwthreads I38 which are externally formed on an elongated internaladjusting and shut-off member in the form of a rod I40. The threads I38on the rod I40 provide relatively sharp V-shaped troughs I42therebetween and have relatively flat crest portions I44. These threadsI38 are similar to the threads 40 in the form of the invention shown inFigs. 1 to 4, inclusive, and may be formed by a similar process, as forexample by a cutting operation followed by a grinding operation aspreviously described.

The registry of the flat crest portions I44 of the threads I38 with thetrough-s I34 provided by the teeth I32 provides a slender, elongated,spiral capillary path or passage I45 for the flow of refrigerant whichis generally triangular in cross section.

As is the case in connection with the form of the invention shown inFigs. 1 to 4 inclusive, the extent of threaded reception of the threadedportion of the rod I40 within the threaded bore II8 determines theextent of the spiral passage I45 and consequently the degree ofrestriction offered to the flow of refrigerant through the device I I0.

In order to increase or decrease the extent of the spiral passage I45the unthreaded portion of the rod I40 projects axially as at I43 fromthe inlet end of the cylinder I I6 and is provided with a flattened orotherwise deformed end I41 which, with the aid of a suitable tool suchas a wrench, may be turned in one direction or the other to .decrease orincrease the threaded extent of the rod within the bore IIS of thecylinder I I5. The Lextreme end of the cylinder IIS may be relievedinternally as at I46 to provide an internal conical ;surface adapted toseat thereagainst a wedge ,shaped ring-like sealing washer I48 which isclamped thereagainst by means of a sealing cap I50, threadedly receivedon the end of the cylinder H5. The sealing washer I48 and cap memberI50, in addition to their scaling function, provides a centering devicefor the outer end regions of the rod I40 to maintain the rod centered inthe counter-bore I20. These members also, in effect, provide a lockingmeans for anchoring the rod I40 in any desired position of adjustment.With the sealing cap I50 tightly and threadedly received upon the end ofthe cylinder H6 and with the sealing washer I48 under compression, therod is frictionally held against turning movement thereof. Thus, when itis desired to effect adjustment of the threaded extent of the rod I40within the cylinder I'I6, it is necessary to unloosen the cap memberI50, after which adjustment the cap member may again be tightened.

The internal diameter of the counter-bore I20 is slightly in excess ofthe external diameter of the unthreaded portion of the rod I40, thuspro- III) viding an annular chamber or path for the flow of fluid fromthe inlet port I28 to the spiral passage I45. I

The inner end of the rod I40, i. e. the end thereof adjacent the outletport I22, is provided with a smooth unthreaded portion I5I of a diametersubstantially equal to the maximum internal diameter of the internallythreaded portion I I8 of the cylinder H6. The extreme inner end of therod I40 is beveled as at I52 to provide a seating surface designed forcooperation with the intern-a1 conical seating surface I26 formed in thecylinder H6 and which surrounds the outlet port I22.

From the above description of parts it will be seen that when the rodI40 is turned in a direction to increase the extent of its threadedreception within the threaded bore II8 of the cylinder IIB the conicalseating surface I52 on the extreme inner end of the rod I40 will bemoved toward the conical seating surface I26 provided in the cylinder H6and surrounding the outlet port I22, while turning movement of the rodI40 in the opposite direction will move the seating surface I52 awayfrom the seating surface I26. The relative positions of the two seatingsurfaces I52 and I26 afford no appreciable restricting function to theflow of fluid through the device IIO except insofar as complete shut offof fluid flow is concerned. Restriction to the flow of fluid through thedevice is dependent entirely upon the adjusted length of the spiralcapillary fluid passage I45 and the overall cross section-a1 dimensionof this fluid path is so extremely small that the flow of fluid throughthis path is not affected by any relative positioning of the seatingsurfaces I52 and I56 until such time as these two surfaces engage eachother in sealing relationship and completely shut off the flow of fluidthrough the device.

The operation of the fluid restricting device H0 is similar to theoperation of the device I0 illustrated in Figs. 1 to 4, inclusive, andrefrigerant under pressure issuing from the tube of conduit I30 entersthe inlet port I20 of the cylinder H6 and passes through the annularspace existing between the counter-bore I20 and the unthreaded outersurface of the rod I40 from whence it passes to the spiral capillaryrestricted passage I45. The pressure of the refrigerant is reducedprogressively as the refrigerant flows through the passage I45 and theamount of pressure drop across the passage is of course deter mined bythe depth of penetration of the threaded portion of the rod I40 into thethreaded bore II8 of the cylinder II6. As the liquid refrigerant reachesthe outlet end of the spiral passage I45 it then enters the spiralpassage afforded by the trough portions I44 existing between the teethI32 and the smooth outer surface portion I5I provided on the rod I40. Aslight amount of expansion of the refrigerant may occur in thisrelatively short spiral passage existing at the inner end of the rod I40and after the liquid has passed through this spiral passage it thenstill further expands into that interior portion of the threaded bore II8 not occupied by the rod I40, as well as expanding into the regionafforded by the outlet port I42 and into the expansion coils I I4.

The expanded refrigerant thus is converted into its gaseous state as itflows through the expansion coil II4 so that heat is absorbed from thesurrounding atmosphere in the usual manner.

The restricting device H0 in the form of the invention disclosed inFigs. 5 to 8, inclusive. ai-

fords a relatively simple means for effectively sealing off the flow ofrefrigerant through the device during such time as assembledrefrigerating units as, for example, household refrigerators, deepfreeze units, and the like embodying the principles of the presentinvention are in transit from the factory to the distributor or from thedistributor to the scene of installation. When the rod M is receivedwithin the threaded bore H8 to the fullest threaded extent of which itis capable with the seating surface I52 bearing against the seatingsurface ['26, flow of the refrigerant through the spiral passage I45 iscompletely shut off and the unit may be shipped or otherwise handled intransit without danger of loss of refrigerant in the event that any ofthe communicating joints of the system become loosened or uncoupled.When the unit arrives at the scene of installation it is merelynecessary for the installation worker or even the user to apply asuitable tool to the deformed end I41 of the rod I40 and turn the latterin such a direc tion as to relieve the seal existing between the seatingsurfaces 152 and I26, after which the system may be put into operationand the extent of threaded reception of the rod I40 in the threaded boreH8 adjusted to attain the most efficient rate of fluid flow through thesystem.

A further feature and advantage of the invention lies in the flushingcapabilities thereof. When foreign matter in the refrigerant tends toclog the restricting passage, it is merely necessary to withdraw the rodI40 by unscrewing substantially halfway, whereupon the pressure of therefrigerant fluid will flush the device and force the foreign materialtherethrough.

Changes may be made in the form, construction and arrangement of partsfrom those disclosed herein without departing in any way from the spiritof the invention or sacrificing any of the attendant advantages thereof,provided, however, that such changes fall within the scope of the claimappended hereto.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

A pressure reducing device for controlling the flow of refrigerantfluids in a refrigeration system comprising an elongated tubular memberhaving an inlet and an outlet at opposite ends thereof, an axial bore ofsubstantially constant diameter extending inwardly through said tubularmember from the outlet end thereof for a predetermined distance, anaxial counterbore within said tubular member of larger diameter thansaid first bore and communicating therewith, said counterbore extendingthrough said tubular member at the inlet end thereof having a lateralinlet port, a set of continuous internal screw threads of constantdiameter formed in said first bore, an elongated adjustable member ofsubstantially constant diameter extending through said counterbore andsaid bore, at least a portion of said adjustable member having a set ofcontinuous external screw threads of constant diameter threadedlyengaging the internal screw threads in said bore, the crests of one ofsaid sets of screw threads being flattened uniformly throughout thelength thereof to provide a spiral passage of uniform cross sectionbetween the sets of screw threads, said adjustable member being movableaxially of said first bore to vary the effective length of said spiralpassage, said tubular member being formed with an inwardly facing valveseat around said outlet, and said adjustable member having oneunthreaded portion extending through the counterbore and outwardlybeyond the inlet of said tubular member and another unthreaded portionadjacent said outlet terminating in a reduced end complementallyengageable with said valve seat to stop fluid flow through the device, awedge-shaped sealing washer within the inlet end of said tubular membersurrounding and engaging the adjacent unthreaded portion of saidadjustable member, and means for releasably engaging said sealing washerand wedging the sealing washer tightly between the said adjustablemember and the adjacent end of said counterbore to lock the adjustablemember and said last named means against movement.

HERMAN M. GOLDBERG.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Date

